COLONIES 



19 



the scales of fishes, the armour of the armadillo, and the thick 

 skin of the crocodile. But in man the skin is so soft that a 

 female mosquito sinks her proboscis into it as easily as a 

 butter-knife cuts into butter. The male mosquito is a feebler 

 organism and its proboscis cannot penetrate the human 

 epidermis. 



Colonies 



We have seen that when the Amoeba is dividing, the two 

 halves are united by a bridge or waist, and for a time the 

 organism is bi-cellular with two nuclei. But in higher Protozoa 

 the bridge may not be broken, and if each of the new cells 



Fig. 6. Volvox aureus Ehrenb. A colony of the second order. ( x210.) 



divide again we have an organism of four similar cells, and 

 if these four divide we have organisms of eight and then 

 of sixteen cells, and so on. Thus we arrive at a multi-ccl hilar 

 organism which, if we regard each cell as an individual, forms 

 a colony. Now there are three orders of colonics. The first 



2-2 



